The present invention relates to a polyurea macromer (PUM), which is useful in the preparation of aqueous dispersions of a variety of emulsion polymers.
Aqueous dispersions of acrylic polymers and polyurethanes generally serve similar market segments. Polyurethane dispersions (PUDs) typically offer superior balance of film formation, flexibility, and hardness over acrylic dispersions in coatings applications, and a superior balance of toughness, abrasion resistance, and mechanical flexibility in adhesives applications. Acrylics, on the other hand, can provide exceptional exterior durability and chemical resistance more cost effectively than PUDs.
The different performance profiles of PUDs and acrylics can be attributed to significant differences in their polymer chain architecture. The pressure to balance cost and performance has lead PUD users to evaluate PUD/acrylic blends and hybrid, with limited success. (See, for example, R. A. Brown et al., “Comparing and contrasting the properties of urethane/acrylic hybrids with those of corresponding blends of urethane dispersions and acrylic emulsions,” Progress in Organic Coatings 2005, 52 (1), 73-84; and H. T. Lee et al., “Synthesis and properties of aqueous polyurethane/polytert-butylacrylate hybrid dispersions,” Journal of Polymer Research 2005, 12 (4), 271-277; and U.S. Pat. No. 5,650,159.)
It would be an advance in the art to find a cost effective way of achieving the desired properties of acrylics and PUDs.